Iran’s launching of a rocket test in close proximity of a U.S. warship has been deemed “highly provocative,” says a U.S. spokesman, who said the regime ship conducted the test while other commercial traffic was close by.

The launch was carried out in the Strait of Hormuz, an essential waterway for trade, through which ⅓ of all oil is traded by sea.

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The test occurred on Saturday as two U.S ships – the USS Harry S. Truman aircraft carrierand the USS Bulkeley destroyer – were in the area, along with a French frigate, said Cmdr. Kyle Raines, a spokesman for U.S. Central Command.

Iranian soldiers announced they would be conducting the tests just 23 minutes prior to launch, according to reports. Their ships then fired “several unguided rockets” just 1,500 yards away from the U.S. vessels, the CENTCOM spokesman said.

“Firing weapons so close to passing coalition ships and commercial traffic within an internationally recognized maritime traffic lane is unsafe, unprofessional and inconsistent with international maritime law,” said Cmdr. Raines.

“U.S. Navy forces are committed to ensuring the safe and free navigation in the Strait of Hormuz and throughout the region by maintaining a strong presence,” added Commander Kevin Stephens, a spokesman for the U.S. Fifth Fleet. “While most interactions between Iranian forces and the U.S. Navy are professional, safe and routine, this event was not and runs contrary to efforts to ensure freedom of navigation and maritime safety in the global commons.”

The U.S. and French vessels were in the region to support the military coalition fighting against the Islamic State (IS), according to U.S. officials. The Fifth Fleet is headquartered at a U.S. Naval base in Bahrain, where its ships are strategically located to also oversee the sea lanes and combat piracy operations, in addition to the anti-IS operations.

Iranian officials have not yet publicly commented on the incident. State-controlled Tabnak news claimed the western news reports serve to “undermine Iran’s capability to provide regional marine safety,” according to a translation by the New York Times.

Iran and world powers signed a nuclear deal in July. Western forces hoped the regime could utilize the agreement to re-engage with the world, but since then, Iran has conducted illegal ballistic missile tests, and continues to aid and arm terrorist organizations worldwide.